Dispersion adhesives

ABSTRACT

The invention relates to the use of aqueous dispersion adhesives on the basis of a mixture of aqueous polyurethane or polyurethane-urea dispersions for bonding foam substrates according to the spray coagulation method.

The invention relates to the use of aqueous dispersion adhesives basedon a mixture of aqueous polyurethane or polyurethane-urea dispersionsfor the adhesive bonding of foam substrates by the spray coagulationprocess.

When adhesively bonding foam substrates to other substrates, for examplefor the combinations foam-foam, foam-wood and foam-plastic, use ispredominantly made of polychloroprene dispersion adhesives in the spraycoagulation process. In this process, the adhesive and a coagulant areconveyed separately into a spray gun, mixed in the spray jet andcoagulated. As the mixing does not take place until in the spray jet, nopot life needs to be taken into account. In addition, the coagulatedadhesive remains on the substrate surface to be adhesively bonded andonly diffuses to a minor extent, if at all, into the pore structure ofthe foam substrates. High initial strengths, sufficiently long opentimes and good heat resistances are frequently achieved.

Important fields of application are the production of mattresses andseating furniture. In particular from Scandinavian countries, there is ademand for chlorine-free alternatives to the polychloroprene dispersionadhesives, in order for example to be able to satisfy the requirementsof the Nordic Ecolabel (type I environmental label according to ISO14024). In addition, they should feature high initial strengths and asufficiently long open time.

Adhesives based on aqueous polyurethane dispersions have becomeestablished worldwide in demanding industrial applications, for examplein the case of shoe manufacturing, the bonding of parts for motorvehicle interiors, sheet lamination or the adhesive bonding of textilesubstrates.

In the case of the use of such dispersions for bonding substrates, thisis usually carried out after the heat-activation process. In this case,the dispersion is applied to the substrate and, after completeevaporation of the water, the adhesive layer is activated by heating,for example using an infrared radiator, and is converted into anadhesive state. The temperature at which the adhesive film becomessticky is referred to as the activation temperature.

However, when using polyurethane or polyurethane-polyurea dispersions,the process of wet bonding can also be used, that is to say the adhesivebonding is effected immediately after application of the adhesive.Mechanical securing of the parts to be joined is necessary until theadhesive has set. This process is often used for the adhesive bonding ofwood or textile substrates.

Both the heat activation process and the wet bonding process are oflimited suitability for the adhesive bonding of foam substrates. Theslow evaporation of the water, in particular, requires long waitingtimes between application of the adhesive and the bonding process, orappropriate drying installations. In addition, a not insignificantportion of the adhesive can diffuse into the pores of the foamsubstrates prior to or during the drying and is then no longer availablefor the actual bonding.

The adhesives based on aqueous polyurethane dispersions which areestablished on the market are generally not suitable for the use of thespray coagulation process since they either do not coagulatesufficiently rapidly, do not have sufficient initial strengths, or, as aresult of the crystallinity of the polymers, form very hard bond seamswhich are unacceptable in particular for mattress production. The opentime, that is to say the time period between application of the adhesiveuntil joining together the parts to be joined, during which asufficiently good bonded connection is still obtained, is generally onlyone minute. For many bonding processes, however, at least twice as muchtime is required.

WO 2013/053786 A1 describes aqueous polyurethane dispersions, thepolymer of which has a melting temperature in the range from 30° C. to50° C., determined by differential scanning calorimetry in accordancewith DIN 65467 at a heating rate of 20 K/min, wherein the polymer isobtainable from two dissimilarly crystallizing polyester polyols inspecified quantitative ratios. These polyurethane dispersions areprimarily suitable as cold contact adhesives, but can also be employedusing spray coagulation processes. However, the initial strengthsachievable thereby are insufficient for most foam bonding applications.

Luphen® D DS 3548 from BASF AG (Ludwigshafen, Germany) provides an epoxyresin-modified polyurethane dispersion which inter alia is reportedlyalso suitable for the spray coagulation process. The basis of the epoxyresin used here is bisphenol A diglycidyl ether. Since bisphenol A andthe conversion products formed therefrom are viewed in an extremelycritical manner in particular by end consumers in respect of a possibleeffect on the endocrine system and accordingly are generally rejected,the market is demanding adhesives and other products which are free frombisphenol A.

WO 2014/182170 A1 describes performing the spray coagulation processusing a particular airless spray process. To this end, mixtures both ofpolychloroprene dispersions and tackifier dispersions and also ofpolyurethane dispersions and tackifier dispersions are used. However,these are not specified further in this document. Fields of applicationmentioned are foam adhesive bonds in the mattress and furnituremanufacturing sector. However, this prior art does not disclose eitherthe nature of the polyurethane dispersions used nor the measures whichcan be taken to ensure a high initial strength and a sufficiently longopen time.

The object of the present invention was therefore that of providing achlorine- and bisphenol A-free alternative to polychloroprene dispersionadhesives for the adhesive bonding of foam substrates by the spraycoagulation process which does not exhibit the disadvantages of theprior art and which features high initial strengths and a sufficientlylong open time of at least 2 minutes.

EP 2 090 603 A2 discloses aqueous dispersions containing a mixture of

A) an aqueous polyurethane or polyurethane-urea dispersion containing

-   -   I. a polymer A) formed from        -   I (i). at least one difunctional aliphatic polyester polyol            having a molecular weight of 400 to 5000 g/mol,        -   I (ii). at least one mixture of hexamethylene diisocyanate            (HDI) and            1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane            (IPDI), and        -   I (iii). at least one mixture of two or more aminic chain            extenders, wherein at least one compound bears an ionic            group,        -   and the polymer A) after drying is semicrystalline or            crystalline with a glass transition at a glass transition            temperature Tg of between −65° C. and −40° C.,

B) an aqueous polyurethane or polyurethane-urea dispersion which differsfrom A) and contains

-   -   II. a polymer B) formed from        -   II (i). at least one difunctional aromatic polyester polyol            having a molecular weight of 400 to 5000 g/mol,        -   II (ii). at least one difunctional polyol component having a            molecular weight of 62 to 399,        -   II (iii). at least one aliphatic diisocyanate and        -   II (iv). at least one aminic chain extender having an ionic            group,        -   wherein the polymer B) after drying is amorphous with a            glass transition at a glass transition temperature Tg of            between −15° C. and +10°.

According to EP 2 090 603 A2, the described mixtures of aqueouspolyurethane or polyurethane-polyurea dispersions are suitable asadhesives both according to the heat activation process and according tothe wet bonding process, and display bond strengths that are better thanthe individual components.

Surprisingly, it has now been found that the mixtures of aqueouspolyurethane or polyurethane-polyurea dispersions which are described inEP 2 090 603 A2 are also outstandingly suitable for the adhesive bondingof foam substrates by the spray coagulation process, provided thatdefined quantitative ratios are complied with:

The present invention therefore provides for the use of aqueousdispersions containing a mixture of

A) an aqueous polyurethane or polyurethane-urea dispersion containing

-   -   I. a polymer A) formed from        -   I (i). at least one difunctional aliphatic polyester polyol            having a molecular weight of 400 to 5000 g/mol,        -   I (ii). at least one mixture of hexamethylene diisocyanate            (HDI) and            1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane            (IPDI), and        -   I (iii). at least one mixture of two or more aminic chain            extenders, wherein at least one compound bears an ionic            group,        -   and the polymer A) after drying is semicrystalline or            crystalline with a glass transition at a glass transition            temperature Tg of between −65° C. and −40° C., and

B) an aqueous polyurethane or polyurethane-urea dispersion which differsfrom A) and contains

-   -   II. a polymer B) formed from        -   II (i). at least one difunctional aromatic polyester polyol            having a molecular weight of 400 to 5000 g/mol,        -   II (ii). at least one difunctional polyol component having a            molecular weight of 62 to 399,        -   II (iii). at least one aliphatic diisocyanate and        -   II (iv). at least one aminic chain extender having an ionic            group,        -   wherein the polymer B) after drying is amorphous with a            glass transition at a glass transition temperature Tg of            between −15° C. and +10° C.;            and wherein the mixture contains 34.8% to 90.2% by weight of            polymer A) and 9.8% to 65.2% by weight of polymer B),            for the adhesive bonding of foam substrates by the spray            coagulation process.

The dispersions referred to as polyurethane dispersions in connectionwith the present invention contain as disperse phase polymers which maybe polyurethanes in the narrower sense, that is to say those polymerswhich are obtained by polymerization of polyols and polyisocyanates, butthey may also be those in which monoamines and/or diamines are used asformation components, possibly as chain extenders. The dispersions thatcan be used according to the invention are therefore referred to asaqueous polyurethane or polyurethane-urea dispersions.

In the spray coagulation process, the aqueous adhesive dispersions andalso a coagulant are conveyed separately into a two-component spray gunand mixed in the spray jet. Spraying is typically effected usingatomizer air at 0.1-5 bar of pressure; however, it is also possible todeliver at least one of the two components airlessly, as described forexample in WO 2015/137808. The coagulation of the dispersion takes placein the spray jet on the path to the surface of the first substrate; aportion of the water present in the adhesive dispersion alreadyevaporates in the process. On impact, the adhesive polymer forms on thesurface of the first substrate a film which is immediately tacky in thestill-wet state. As the mixing of adhesive dispersion and coagulant doesnot take place until in the spray jet, no pot life needs to be takeninto account. On account of the tackiness of the polymer film in the wetstate, the second surface can be immediately joined, ideally for examplewith pressure on the substrates towards the adhesive surface. Theapplication of pressure by pressing the two substrate surfaces togetheris advantageous since it increases the strength of the bond. It islikewise advantageous when at least one of the two substrates is porousor permeable to water, in order to allow for the transport of water awayout of the solidifying adhesive joint.

Suitable coagulants include aqueous solutions of salts, preferably ofmetals of the first, second and third main group of the Periodic Table,in particular if they exhibit a good water solubility. Salts based ondivalent or trivalent cations are preferably used. Particular preferenceis given to using calcium chloride, zinc sulfate or aluminum sulfate.Very particular preference is given to using calcium chloride. Mixturesof different salts as per the above description can also be used as theaqueous solution.

The concentration of the salts in the aqueous salt solutions suitable ascoagulant is 1% to 20% by weight, preferably 2% to 10% by weight andparticularly preferably 3% to 4% by weight. The proportion of theaqueous solution of the coagulant, based on the sum of adhesive solutionplus coagulant solution, is between 0.1% and 50% by weight, preferablybetween 1% and 30% by weight, particularly preferably between 8% and 20%by weight and very particularly preferably between 12% and 18% byweight.

Alternatively, coagulants used may also be aqueous solutions ofinorganic or organic acids, preferably citric acid, phosphoric acid orcarbonic acid, and mixtures of one or more of the abovementioned saltswith one or more of these acids.

The dispersions used according to the invention in each case generallycontain 30% to 55% by weight of solids, preferably 38% to 52% by weight.Based on the polymers A) and B) present as disperse phase in thedispersions, the mixtures according to the invention contain 34.8% to90.2% by weight of polymer A) and 9.8% to 65.2% by weight of polymer B),preferably 44.4% to 87.8% by weight of polymer A) and 12.2% to 55.6% byweight of polymer B), particularly preferably 54.5% to 81.9% by weightof polymer A) and 18.1% to 45.5% by weight of polymer B), and veryparticularly preferably 65.1% to 81.9% by weight of polymer A) and 18.1%to 34.9% by weight of polymer B), based on the total weight of polymericsolids A) and B).

Suitable difunctional aliphatic polyester polyols A) I(i). which can beused include in particular linear polyester diols as can be prepared ina known manner from aliphatic or cycloaliphatic dicarboxylic acids, suchas for example succinic, methylsuccinic, glutaric, adipic, pimelic,suberic, azelaic, sebacic, nonanedicarboxylic, decanedicarboxylic,tetrahydrophthalic, hexahydrophthalic, cyclohexanedicarboxylic, maleic,fumaric, malonic or mixtures thereof with polyhydric alcohols such asfor example ethanediol, di-, tri-, or tetraethylene glycol,propane-1,2-diol, di-, tri-, or tetrapropylene glycol, propane-1,3-diol,butane-1,4-diol, butane-1,3-diol, butane-2,3-diol, pentane-1,5-diol,hexane-1,6-diol, 2,2-dimethylpropane-1,3-diol, 1,4-dihydroxycyclohexane,1,4-dimethylolcyclohexane, octane-1,8-diol, decane-1,10-diol,dodecane-1,12-diol or mixtures thereof.

Instead of the free polycarboxylic acid, the correspondingpolycarboxylic anhydrides or corresponding polycarboxylic esters oflower alcohols or mixtures thereof can also be used to produce thepolyesters.

Preference is given to difunctional aliphatic polyester polyols A) I(i).based on succinic acid, methylsuccinic acid, glutaric acid, adipic acidor maleic acid and propane-1,3-diol, butane-1,4-diol or hexane-1,6-diol.

Particular preference is given to difunctional aliphatic polyesterpolyols A) I(i). based on adipic acid and butane-1,4-diol orhexane-1,6-diol.

Very particular preference is given to difunctional aliphatic polyesterpolyols A) I(i). based on adipic acid and butane-1,4-diol.

The molecular weight of the difunctional aliphatic polyester polyol A)I(i). is between 400 and 5000 g/mol, preferably between 1500 and 3000g/mol, particularly preferably between 1900 and 2500 g/mol, veryparticularly preferably between 2100 and 2300 g/mol.

The isocyanate component A) I(ii). used is a mixture of hexamethylenediisocyanate (HDI) and1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). TheHDI:IPDI molar ratio is preferably between 9:1 and 1:9, particularlypreferably between 3:1 and 1:3, it is very particularly preferably 2:1.

The component A) I(iii). consists of a mixture of two or more aminicchain extenders, wherein at least one compound bears an ionic group. Inthe context of the invention, chain extenders also include monoamineswhich lead to chain termination.

Examples of monoamines are aliphatic and/or alicyclic primary and/orsecondary monoamines such as ethylamine, diethylamine, the isomericpropyl- and butylamines, higher linear aliphatic monoamines andcycloaliphatic monoamines such as cyclohexylamine. Further examples areaminoalcohols, i.e. compounds containing amino and hydroxyl groups inone molecule, such as for example ethanolamine, N-methylethanolamine,diethanolamine or 2-propanolamine. Further examples are monoaminocompounds which additionally bear sulfonic acid and/or carboxyl groups,such as for example taurine, glycine or alanine.

Examples of diamino compounds are ethane-1,2-diamine,hexamethylene-1,6-diamine,1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (isophoronediamine),piperazine, 1,4-diaminocyclohexane or bis(4-aminocyclohexyl)methane.Adipic dihydrazide, hydrazine and hydrazine hydrate are furthermoresuitable. Polyamines such as diethylenetriamine may also be used asformation component instead of a diamino compound.

Further examples are aminoalcohols, i.e. compounds containing amino andhydroxyl groups in one molecule, such as for example1,3-diamino-2-propanol, N-(2-hydroxyethyl)ethylenediamine orN,N-bis(2-hydroxyethyl)ethylenediamine.

Examples of diamino compounds having an ionic group, which thereforeadditionally bear sulfonate and/or carboxylate groups, include forexample the sodium or potassium salts ofN-(2-aminoethyl)-2-aminoethanesulfonic acid/-carboxylic acid, ofN-(3-aminopropyl)-2-aminoethanesulfonic acid/-carboxylic acid, ofN-(3-aminopropyl)-3-aminopropanesulfonic acid/carboxylic acid or ofN-(2-aminoethyl)-3-aminopropanesulfonic acid/-carboxylic acid.Preference is given to the sodium salt ofN-(2-aminoethyl)-2-aminoethanesulfonic acid.

Preferred constituents of the mixture A) I(iii). are diethanolamine,ethane-1,2-diamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane(isophoronediamine), piperazine, N-(2-hydroxyethyl)ethylenediamine andthe sodium salts of N-(2-aminoethyl)-2-aminoethanesulfonicacid/-carboxylic acid.

Particular preference is given to a mixture of diethanolamine and thesodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid.

The polymer A) after drying is semicrystalline or crystalline with aglass transition at a glass transition temperature Tg of between −65° C.and −40° C., preferably with a Tg of between −60° C. and −45° C.,particularly preferably of between −55° C. and −50° C.

The polymer A) is referred to as semicrystalline or crystalline when, inDSC measurement in accordance with DIN 65467 at a heating rate of 20K/min, it has a melting peak which corresponds to an enthalpy offusion >5 J/g, preferably >10 J/g, particularly preferably >20 J/g andvery particularly preferably >40 J/g. The melting peak is caused by themelting of regular substructures in the polymer. The melting temperatureis in this case preferably in a range between 30° C. and 80° C.,particularly preferably between 40° C. and 70° C., very particularlypreferably between 42° C. and 55° C. The first heating is evaluated inorder to also detect polymers which crystallize slowly.

The polymer B) is referred to as amorphous when, during the firstheating, it does not have a melting peak or only has a melting peak withan enthalpy of fusion <5 J/g, preferably <3 J/g, particularly preferably<1 J/g.

In a preferred embodiment of the invention, the amorphous polymer B)does not have a melting peak.

Suitable difunctional aromatic polyester polyols B) II(i). in particularinclude linear polyester diols as may be prepared in a known manner fromaromatic dicarboxylic acids, such as for example terephthalic,isophthalic or o-phthalic acid and also acid anhydrides thereof, such asfor example o-phthalic anhydride, with polyhydric alcohols, such as forexample ethanediol, di-, tri-, or tetraethylene glycol,propane-1,2-diol, di-, tri-, or tetrapropylene glycol, propane-1,3-diol,butane-1,4-diol, butane-1,3-diol, butane-2,3-diol, pentane-1,5-diol,hexane-1,6-diol, 2,2-dimethylpropane-1,3-diol, 1,4-dihydroxycyclohexane,1,4-dimethylolcyclohexane, octane-1,8-diol, decane-1,10-diol,dodecane-1,12-diol or mixtures of these.

Preference is given to difunctional aromatic polyester polyols B) II(i).based on o-phthalic acid, o-phthalic anhydride and butane-1,4-diol orhexane-1,6-diol.

Particular preference is given to difunctional aromatic polyesterpolyols B) II(i). based on o-phthalic acid or o-phthalic anhydride andhexane-1,6-diol.

The molecular weight of the difunctional aromatic polyester polyol B)II(i). is between 400 and 5000 g/mol, preferably between 1500 and 3000g/mol, particularly preferably between 1800 and 2300 g/mol, veryparticularly preferably between 1900 and 2100 g/mol.

Examples of difunctional polyol components having a molecular weight of62 to 399 and which are suitable as formation component B) II(ii). arethe products listed under A) I(i). and B) II(i)., provided they have amolecular weight of 62 to 399 daltons. Further suitable components arethe polyhydric, in particular dihydric, alcohols cited for thepreparation of the polyester polyols and also further low molecularweight polyester diols such as for example bis(hydroxyethyl) adipate.Also suitable are short-chain difunctional polyether polyols such as forexample the homopolymers, copolymers and graft polymers of ethyleneoxide or of propylene oxide.

Preferred formation components B) II(ii). are butane-1,4-diol andhexane-1,6-diol, and hexane-1,6-diol is particularly preferred.

Suitable formation components B) II(iii). are any desired aliphaticcompounds having at least two free isocyanate groups per molecule.Preference is given to using diisocyanates Y(NCO)₂, where Y is adivalent aliphatic hydrocarbon radical having 4 to 12 carbon atoms or adivalent cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms.Examples of such diisocyanates which are preferably to be used includetetramethylene diisocyanate, methylpentamethylene diisocyanate,hexamethylene diisocyanate, dodecamethylene diisocyanate,1,4-diisocyanatocyclohexane,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane,4,4′-diisocyanatodicyclohexylmethane or4,4′-diisocyanato-2,2-dicyclohexylpropane, or mixtures thereof.

Particular preference is given to hexamethylene diisocyanate (HDI),1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) and4,4′-diisocyanatodicyclohexylmethane, and mixtures thereof. However, theisocyanates are preferably used alone.

Very particular preference is given to hexamethylene diisocyanate (HDI).

Aminic chain extenders B) II(vi). having an ionic group are preferablydiamino compounds which additionally bear sulfonate and/or carboxylategroups, such as for example the sodium or potassium salts ofN-(2-aminoethyl)-2-aminoethanesulfonic acid, ofN-(3-aminopropyl)-2-aminoethanesulfonic acid, ofN-(3-aminopropyl)-3-aminopropanesulfonic acid, ofN-(2-aminoethyl)-3-aminopropanesulfonic acid, or of the analogouscarboxylic acids.

Particular preference is given to the sodium salts ofN-(2-aminoethyl)-2-aminoethanesulfonic acid and of the analogouscarboxylic acid, very particular preference is given to the sodium saltof N-(2-aminoethyl)-2-aminoethanesulfonic acid.

The aminic chain extenders B) II(iv). having an ionic group may be usedalone or together with other aminic chain extenders as have beendescribed for example under A) I(iii). They are preferably used alone.

The polymer B) after drying is amorphous with a glass transition at aglass transition temperature Tg of between −15° C. and +10° C.,preferably with a Tg of between −10° C. and +5° C., particularlypreferably of between −5° C. and 0° C.

The aqueous polyurethane or polyurethane-urea dispersions containing thepolymers A) or B) have a solids content of 10% to 70% by weight,preferably of 25% to 60% by weight and particularly preferably of 35% to55% by weight.

The aqueous polyurethane or polyurethane-urea dispersions containing thepolymers A) or B) are preferably prepared by the acetone process. Tothis end, prepolymers are prepared from the components A) I(i). and A)I(ii)., and respectively from B) II(i)., B) II(ii). and B) II(iii)., aredissolved in acetone and are chain-extended with the components A)I(iii). and, respectively, B) II(iv). The acetone is distilled off afterdispersing with water. The application and performance of the acetoneprocess is prior art and is known to those skilled in the art.

The aqueous polyurethane or polyurethane-urea dispersions containing thepolymers A) or B) and the mixtures according to the invention preferablydo not contain any external emulsifiers.

The dispersions according to the invention are preferably prepared bymixing the aqueous polyurethane or polyurethane or polyurethane-ureadispersions of polymers A) and B).

The adhesive bonds produced with the dispersions according to theinvention by the spray coagulation process display sufficient immediatestrengths before instantaneous tearing of the material, with an opentime of at least 3 minutes. In particular when adhesively bonding foamon foam or foam on other substrate surfaces, such as for example wood,metal or plastic, which have a three-dimensional structure and hence arenot flat, the adhesive bonds produced by the process according to theinvention are capable of absorbing the restoring forces of the foamwithout a waiting time, in particular without the complete removal ofthe water. An example of such an application is the adhesive bonding ofcuboid foam blocks to form cushions by bending the narrow side surfacesand, after the spray application of the adhesive dispersion according tothe invention, immediately pressing them against one another while wet.Thanks to the high immediate wet strength, the applied pressure can beimmediately released again without the strained foam springing back orshifting.

In particular, the dispersions according to the invention are used toproduce adhesive compositions which are suitable for the production ofadhesive composites where the adhesive composite comprises a substrate,the dispersion according to the invention, and a further substrate. Thetwo substrates can consist of the same or different materials. Bydefinition, the substrates can also be sheet-like structures. The atleast one substrate is preferably a foam substrate.

A foam substrate is understood to mean a substrate made of foam, foamsgenerally being synthetically produced substances having a cellularstructure and low density. A distinction can be made here betweenopen-cell, closed-cell and mixed-cell foams. Depending on the hardness,foams are divided into rigid and flexible foams. Virtually all plasticsare suitable for foaming.

In principle, the dispersions according to the invention are suitablefor the adhesive bonding of all foam substrates by the spray coagulationprocess. Preference is given to adhesively bonding open-cell andmixed-cell foam substrates.

In a preferred embodiment of the invention, the foam substrate(s) is/arecomposed of polyurethane (for example polyether and polyester foams)and/or a rubber, such as for example natural rubber (NR),styrene-butadiene rubber (SBR), ethylene-propylene-diene polymer (EPDM),butadiene-acrylonitrile rubber (NBR) or chloroprene rubber (CR).

In a particularly preferred embodiment of the invention, the foamsubstrate(s) is/are composed of polyurethane.

The dispersions according to the invention moreover feature goodadhesion to a very wide variety of other substrates, such as for exampleto wood, paper, leather, textiles, cork, and plastics (thermoplastics,elastomers, thermosets, composites) such as different polyvinyl chloridequalities, polyurethanes, polyvinyl acetate, ABS, rubbers,poly(ethylene-vinyl acetate), polycarbonate or polyolefins, such as forexample filled or unfilled polypropylene. In rare cases, pretreatment ofthe substrate surface is necessary, for example by priming, singeing orcorona treatment, in particular in the case of nonpolar substrates.

The adhesive compositions, containing the dispersions according to theinvention, are thus suitable for the adhesive bonding of any desiredsubstrates, preferably formed from the abovementioned materials.

The adhesives according to the invention are particularly suitable forthe bonding of foam on foam, foam on wood, foam on various plastics, andof textiles on various substrates.

An adhesive composite comprising substrates and sheet-like structuresadhesively bonded with the dispersions used according to the inventionis also subject matter of the present application, as areadhesive-joined foam substrates which are obtained by the use accordingto the invention.

EXAMPLES

The invention will be elucidated in more detail below on the basis ofthe examples. The following methods and test methods were used here:

A) Spray Coagulation Process:

A standard spray gun for two-component dispersion adhesives, namely thePILOT III 2K from Walther Pilot, is used for application. The adhesiveand the coagulant CaCl₂ (3% by weight solution in water) are conveyedseparately into the spray gun, mixed in the spray jet and the adhesiveis coagulated. As the mixing does not take place until in the spray jet,no pot life needs to be taken into account. A ratio of 86% by weightadhesive dispersion and 14% by weight CaCl₂ solution was chosen.

The precise settings of the spray gun are known in principle to theperson skilled in the art and can be tailored to the specific casewithout undue burden and determined by simple preliminary experiments.The quantitative ratios and the application weight can be determined byreweighing the reservoir vessel and the substrates.

The following settings were used:

-   -   a.) Adhesive component: conveying pressure 1.3 bar    -   b.) Coagulation component: conveying pressure 0.3 bar    -   c.) Atomizer air pressure: 2.8 bar    -   d.) Bore diameter (nozzle) for adhesive component: 1.0 mm    -   e.) Bore diameter (nozzle) for coagulant component: 0.4 mm    -   f.) Application weights: 130-150 g/m² (wet)

B) Determination of the Initial Strength:

As test material, ST 5540 (1) PU foam test specimens from STNSchaumstoff-Technik-Nirnberg GmbH having the dimensions 10×5×3 cm and afoam density of 40 kg/m³ are used (see FIG. 1). For assessment of theinitial strength, immediately after application of the adhesive to theupper side (2) of the foam bodies (1) by the spray coagulation process(application rate 130-150 g/m² wet), the test specimens are folded (4)in the middle with a wooden rod (3) (D=7 mm round wood or 7×7 mmrectangle) and fed by means of the test apparatus (5) through 2 steelrolls (6) (diameter 40 mm, length 64 mm) the tangential spacing (7) ofwhich was previously set to 10 mm using a threaded spindle (8). Theinitial strength is sufficient if the test specimen or the bond seam (9)does not come undone despite the restoring forces present in the testspecimen.

C) Determination of the Open Time

As test material, Recticel T 20120 polyether foam bodies from Recticelhaving the dimensions 10×5×3 cm and a foam density of 20 kg/m³ are used.To assess the open time, the test specimens are folded in the middle andjoined together with light palm pressure immediately, every 60 seconds,or if necessary at time intervals to be defined, after the applicationof adhesive by means of the spray coagulation process (application rate130-150 g/m² wet). The end of the open time is indicated by the strengthno longer sufficing and the test specimen opening as a result of therestoring forces arising.

D) Ascertainment of the Hardness of the Bond Seam:

The bond seam of the test specimen produced under B) was assessed indirect comparison with reference samples sensorially by means of touchafter 24 h of storage at room temperature. The reference samples wereproduced using commercially available polychloroprene latices (CovestroDeutschland AG) having differing Shore A hardness. The bond seam of thetest specimen formed from Dispercoll® C 84 (Shore A hardness of thepure, dried polymer=88) was taken as a reference for a hard bond seam,the bond seam of the test specimen formed from Dispercoll® C 74 (Shore Ahardness of the pure, dried polymer=55) was taken as a reference for abond seam of intermediate hardness and the bond seam of the testspecimen formed from Dispercoll® C 2372 (Shore A hardness of the pure,dried polymer=40) was taken as a reference for a soft bond seam.

E) Ascertainment of the Glass Transition Temperatures, MeltingTemperatures and Enthalpies of Fusion by Means of DSC:

The glass transition temperatures and also melting temperatures andenthalpies of fusion were determined by means of differential scanningcalorimetry (DSC) using a Pyris Diamond DSC calorimeter fromPerkin-Elmer. To this end, a film was produced by knife coating thedispersion onto a glass sheet at a 100 μm wet film thickness, flashedoff for 2 hours, and then this film together with the glass sheet isdried in a dry box for 3 days at room temperature and 0% relative roomhumidity. Then, using 10 mg of sample material from this film, the DSCcurve was recorded with the following measurement conditions: Rapidcooling to the starting temperature −100° C., then commencement of threeheatings from −100° C. to +150° C. at a heating rate of 20 K/min and acooling rate of 320 K/min under a helium atmosphere and with coolingwith liquid nitrogen. The glass transition temperature corresponds tothe temperature at half the height of the glass transition, with thethird heating being assessed. For determination of the meltingtemperatures and enthalpies of fusion, the first heating was assessed.

F) Feedstocks:

-   Polyester I: polyester diol formed from butane-1,4-diol and adipic    acid having an OH number=50-   Polyester II: polyester diol formed from hexane-1,6-diol and    phthalic anhydride having an OH number=56-   Desmodur® H: hexamethylene 1,6-diisocyanate (Covestro Deutschland    AG, Leverkusen/Germany)-   Desmodur® I: isophorone diisocyanate (Covestro Deutschland AG,    Leverkusen/Germany)

Example 1 (According to the Invention)

Preparation of an aqueous polyurethane or polyurethane-urea dispersioncontaining polymer A):

450 g of polyester I are dewatered for 1 hour at 110° C. and 15 mbar. At80° C., 30.11 g of Desmodur® H and then 20.14 g of Desmodur® I areadded. The mixture is stirred at 80 to 90° C. until a constantisocyanate content of 1.15% has been reached. The reaction mixture isdissolved in 750 g of acetone and cooled to 48° C. Into the homogeneoussolution is added a solution of 5.95 g of the sodium salt ofN-(2-aminoethyl)-2-aminoethanesulfonic acid and 2.57 g of diethanolaminein 65 g of water with vigorous stirring. After 30 minutes, the mixtureis dispersed by addition of 700 g of water. Distillative removal of theacetone affords an aqueous polyurethane-polyurea dispersion having asolids content of 40.0% by weight.

The polymer present is semicrystalline after drying with a glasstransition at a glass transition temperature Tg of −54° C., a meltingtemperature of 48° C. and an enthalpy of fusion of 50.4 J/g.

Example 2 (According to the Invention)

Preparation of an aqueous polyurethane or polyurethane-urea dispersioncontaining polymer B):

1215 g of polyester II are dewatered for 1 hour at 110° C. and 15 mbar.At 80° C., 4.6 g of hexane-1,6-diol and 179.0 g of Desmodur® H are addedand the mixture is stirred at 90° C. until a constant isocyanate contentof 2.28% has been reached. The reaction mixture is dissolved in 2490 gof acetone and cooled to 48° C. Into the homogeneous solution is added asolution of 31.9 g of the sodium salt ofN-(2-aminoethyl)-2-aminoethanesulfonic acid in 300 g of water withvigorous stirring. After 30 minutes, the mixture is dispersed byaddition of 1150 g of water. Distillative removal of the acetone affordsan aqueous polyurethane-polyurea dispersion having a solids content of50.0% by weight.

The polymer present is amorphous after drying (does not have a meltingpeak in DSC) and has a glass transition at a glass transitiontemperature Tg of −1.5° C.

Example 3 (Comparison)

Use of the dispersion from example 1 (containing 100% polymer A). As canbe seen from the table, while the initial strength is good, anexcessively hard bond seam is obtained and the open time, at one minute,is insufficient.

Example 4 (Comparison)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

95 parts by weight of the dispersion from example 1 (semicrystalline)and 5 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 93.8% byweight of polymer A and 6.2% by weight of polymer B.

As can be seen from the table, while the initial strength is good, anexcessively hard bond seam is obtained and the open time, at one minute,is insufficient.

Example 5 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

92 parts by weight of the dispersion from example 1 (semicrystalline)and 8 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 90.2% byweight of polymer A and 9.8% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at three minutes,meets requirements.

Example 6 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

90 parts by weight of the dispersion from example 1 (semicrystalline)and 10 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 87.8% byweight of polymer A and 12.2% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at four minutes,meets requirements.

Example 7 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

85 parts by weight of the dispersion from example 1 (semicrystalline)and 15 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 81.9% byweight of polymer A and 18.1% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at 7 minutes, meetsrequirements.

Example 8 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

80 parts by weight of the dispersion from example 1 (semicrystalline)and 20 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 76.2% byweight of polymer A and 23.8% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at 7 minutes, meetsrequirements.

Example 9 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

75 parts by weight of the dispersion from example 1 (semicrystalline)and 25 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 70.6% byweight of polymer A and 29.4% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at 7 minutes, meetsrequirements.

Example 10 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

70 parts by weight of the dispersion from example 1 (semicrystalline)and 30 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 65.1% byweight of polymer A and 34.9% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at 7 minutes, meetsrequirements.

Example 11 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

60 parts by weight of the dispersion from example 1 (semicrystalline)and 40 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 54.5% byweight of polymer A and 45.5% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at 7 minutes, meetsrequirements.

Example 12 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

50 parts by weight of the dispersion from example 1 (semicrystalline)and 50 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 44.4% byweight of polymer A and 55.6% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is of intermediate hardness and the open time, at 4 minutes, meetsrequirements.

Example 13 (According to the Invention)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

40 parts by weight of the dispersion from example 1 (semicrystalline)and 60 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 34.8% byweight of polymer A and 65.2% by weight of polymer B.

As can be seen from the table, the initial strength is good, the bondseam is soft and the open time, at 3 minutes, meets requirements.

Example 14 (Comparison)

Preparation of a mixture according to the invention of the dispersionsof examples 1 and 2 and use:

30 parts by weight of the dispersion from example 1 (semicrystalline)and 70 parts by weight of the dispersion from example 2 (amorphous) aremixed and homogenized with stirring. Taking the solids contents intoconsideration, the mixture according to the invention contains 25.5% byweight of polymer A and 74.5% by weight of polymer B.

As can be seen from the table, there is no initial strength.

Example 15 (Comparison)

Use of the dispersion from example 2 (containing 100% polymer B).

As can be seen from the table below, there is no initial strength.

TABLE Results of the experiments according to the invention and of thecomparative experiments Polymer A/B Initial Hardness of Open timeExample [% by wt.] strength the seam [minutes] 3 (comparison) 100/0  yeshard 1 4 (comparison) 93.8/6.2  yes hard 1 5 (according to the 90.2/9.8 yes intermediate 3 invention) 6 (according to the 87.8/12.2 yesintermediate 4 invention) 7 (according to the 81.9/18.1 yes intermediate7 invention) 8 (according to the 76.2/23.8 yes intermediate 7 invention)9 (according to the 70.6/29.4 yes intermediate 7 invention) 10(according to the 65.1/34.9 yes intermediate 7 invention) 11 (accordingto the 54.5/45.5 yes intermediate 6 invention) 12 (according to the44.4/55.6 yes intermediate 4 invention) 13 (according to the 34.8/65.2yes soft 3 invention) 14 (comparison) 25.5/74.5 no not 0 determinable 15(comparison)  0/100 no not 0 determinable

1-9. (canceled)
 10. An adhesive-bonded foam substrates comprising: afoam substrate; a second substrate; and an adhesive composition appliedto bond the foam substrate to the second substrate, wherein the adhesivecomposition comprises: an aqueous dispersion comprising a mixture of: A)an aqueous polyurethane or polyurethane-urea dispersion comprising I. apolymer A) formed from I (i). at least one difunctional aliphaticpolyester polyol having a molecular weight of 400 to 5000 q/mol, I (ii).at least one mixture of hexamethylene diisocyanate (HDI) and1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), and I(iii). at least one mixture of two or more aminic chain extenders,wherein at least one compound bears an ionic group, and the polymer A)after drying is semicrystalline or crystalline with a glass transitionat a glass transition temperature Tq of between −65° C. and −40° C., andB) an aqueous polyurethane or polyurethane-urea dispersion which differsfrom A) and contains II. a polymer B) formed from II(i). at least onedifunctional aromatic polyester polyol having a molecular weight of 400to 5000 q/mol, II (ii). at least one difunctional polyol componenthaving a molecular weight of 62 to 399, II (iii). at least one aliphaticdiisocyanate and II (iv). at least one aminic chain extender having anionic group, wherein the polymer B) after drying is amorphous with aglass transition at a glass transition temperature Tq of between −15° C.and +10° C.: and wherein the mixture contains 34.8% to 90.2% by weightof polymer A) and 9.8% to 65.2% by weight of polymer B), based on thesum total of polymers A) and B).
 11. The adhesive-bonded foam substrateaccording to claim 10, wherein the second substrate is a second foamsubstrate.
 12. The adhesive-bonded foam substrate according to claim 10,wherein the mixture contains 44.4% to 87.8% by weight of polymer A) and12.2% to 55.6% by weight of polymer B).
 13. The adhesive-bonded foamsubstrate according to claim 10, wherein the mixture contains 54.5% to81.9% by weight of polymer A) and 18.1% to 45.5% by weight of polymerB).
 14. The adhesive-bonded foam substrate according to claim 10,wherein an HDI:IPDI molar ratio is between 9:1 and 1:9.
 15. Theadhesive-bonded foam substrate according to claim 10, wherein anHDI:IPDI molar ratio is between 3:1 and 1:3.
 16. The adhesive-bondedfoam substrate according to claim 10, wherein component A) I(iii). is amixture of diethanolamine and a sodium salt ofN-(2-aminoethyl)-2-aminoethanesulfonic acid.
 17. The adhesive-bondedfoam substrate according to claim 10, wherein component B) II(i). is apolyester polyol based on o-phthalic acid, o-phthalic anhydride andbutane-1,4-diol or hexane-1,6-diol.
 18. A process for preparing anaqueous dispersion, comprising: mixing A) an aqueous polyurethane orpolyurethane-urea dispersion with B) an aqueous polyurethane orpolyurethane-urea dispersion that differs from A) to form a mixture,wherein A) the aqueous polyurethane or polyurethane-urea dispersioncomprises I. a polymer A) formed from I (i). at least one difunctionalaliphatic polyester polyol having a molecular weight of 400 to 5000g/mol, I (ii). at least one mixture of hexamethylene diisocyanate (HDI)and 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI),and I (iii). at least one mixture of two or more aminic chain extenders,wherein at least one compound bears an ionic group, and the polymer A)after drying is semicrystalline or crystalline with a glass transitionat a glass transition temperature Tg of between −65° C. and −40° C., andB) the aqueous polyurethane or polyurethane-urea dispersion that differsfrom A) comprises II. a polymer B) formed from II (i). at least onedifunctional aromatic polyester polyol having a molecular weight of 400to 5000 g/mol, II (ii). at least one difunctional polyol componenthaving a molecular weight of 62 to 399, II (iii). at least one aliphaticdiisocyanate and II (iv). at least one aminic chain extender having anionic group, wherein the polymer B) after drying is amorphous with aglass transition at a glass transition temperature Tg of between −15° C.and +10° C., and wherein the mixture comprises 34.8% to 90.2% by weightof polymer A) and 9.8% to 65.2% by weight of polymer B), based on a sumtotal of polymers A) and B).